The invention concerns a clutch.
In selector gears which are shifted subject to interruption of traction force, i.e. one input shaft is separated from a prime mover by a clutch during the shifting operation, the desired gear can be engaged with a clutch of the above described type by slipping the selector teeth of a sliding sleeve into clutch teeth of a clutch body which is secured to a transmission element to be engaged such as a gearwheel or transmission housing. When engaged, the torque is transmitted from one gear element to another gear element, such as a gear wheel or shaft via the clutch body, the clutch teeth, the selector teeth, the sliding sleeve and the sleeve guide, or supported on the transmission housing. The gear engaged determines the reduction ratio and thus the rotational speed ratio between the input shaft and output shaft of the transmission. The transmission elements not engaged, e.g. the gear wheels of the remaining gears that rotate freely and are permanently engaged, rotate at a differential rotational speed corresponding to their ratio in relation to the transmission elements engaged. When shifting from one gear to another, the parts to be engaged have to be brought during the shifting operation to an almost equal rotational speed before the selector teeth of the sliding sleeve can mesh in the clutch teeth of the clutch body to be shifted.
A synchronizer mechanism serves this purpose. Essentially it consists of friction surfaces, such as a friction cone on the clutch body and friction surfaces such as a counter cone on a synchronizing ring, which in addition, has locking teeth. The synchronizing ring revolves with the sliding sleeve, but can rotate relative to it around a limited rotation angle between two stops in order that a locking device, such as locking teeth, is brought to locking position on the synchronizing ring.
If the sleeve is moved in the direction of the clutch body to be engaged, the synchronizing ring with its counter cone is pressed, via resilient detent means, against the friction cone of the clutch body. At the same time, the synchronizing ring turns relative to the sleeve so that frontside inclined surfaces of the selector teeth hit on corresponding locking surfaces of the locking teeth. Thereby an axial force is exerted on the synchronizing ring and the friction surfaces. The selector force simultaneously produces, via the inclined surfaces, a restoring force on the synchronizing ring. The force exceeds, during synchronous speed of the parts, the peripheral force acting on the friction surfaces and brings the synchronizing ring to a central position in which the sleeve can be cut through.
EP 0 184 077B1 has made known such selector clutches in particular for transmissions in countershaft design. The sliding sleeve is here movably disposed upon an inner sleeve carrier and the synchronizing rings are rotatably axially guided opposite the sleeve carrier around a rotation angle limited by stops. In addition, tangential springs are disposed between the sleeve carrier and the synchronizer ring in a manner such as to press both parts against their stops into neutral position contrary to the direction of motion.
DE 34 44 562 has disclosed a clutch for a planetary step which has synchronizing rings without locking teeth. The synchronizing rings mesh with engaging gears almost over the whole axial extent in the selector teeth of the sliding sleeve without allowing a limited angle of rotation.
The problem on which the invention is based is to make possible in clutches, a locking synchronization even when the sliding sleeve is guided on its external periphery and is very narrow.